El 18/06/15 a les 23:55, Ziv Scully ha escrit:
As far as I can see, the proposed changes do 3 things:
(1) Add a few new things especially for layout (the forall/foreach/etc.
sort of thing).
(2) Make normal XML a bit nicer by eliminating closing tags.
(3) Make XML mixed with Ur/Web "macros" less clunky by eliminating some
extra {} and <xml></xml> pairs.
* First, with structure by indentation with tag autoclosing, the
document tree structure shows clearer.
Check https://hackage.haskell.org/package/hamlet
and
http://www.yesodweb.com/book/shakespearean-templates#shakespearean-templates_hamlet_html
* Second, you can specify conditional subtrees, subject to decision logic
$if cond
subtree1
$elsif cond
subtree2
$else cond
subtree3
---------------
$some pattern
subtree1
$none
subtree2
---------------
$case expression
$of pattern
subtree1
$of pattern
subtree2
See see
http://www.yesodweb.com/book/shakespearean-templates#shakespearean-templates_conditionals
--------------
* Third, you can specify foldMap traversals of foldable containers
$foldmap {items_expr} <| fn {item_pattern} =>
item_subtree
Haskell differentiates between sequentially enforced traversal
(Data.Traversable) and non-enforced (Data.Foldable) as
non-monadic/applicative code exec. order is not granted sequential.
I am not sure about this need in Ur, but in case, an extra logic
statement could be used.
----------
Any other control structure on subtrees can be envisioned as needed.
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